which waterproofing system for new shower?

Plumbing for my new bathroom is almost done. Insulating should go quickly. So, I'm on to thinking about the tile. The shower is 3x4', no tub; tile will probably go to the ceiling. I'll be making a mud bed. What waterproofing system do you guys recommend for a novice? I'd planned on Kerdi, after reading John Bridge's forum. Now I'm not so sure. Our local tile supplier sells Hydroment and Gold Plus. I've heard of RedGard, too.

I've tiled a couple rooms, but never a bathroom. Which system is the best bet for a novice?

John,
All that's done so far is the framing and plumbing rough-in. The shape and dimensions don't work for a store-bought pan, so I figure I'll build it myself. Walls will be 1/2"(?) cement board. Tiles haven't been selected yet, but my wife is leaning towards a subway shaped ceramic. Shower floor tiles will be smaller to accomodate the slope. The fella at the tile store recommended Gold Plus, a roll-on membrane.

If you chose Kerdi, their recommended wall covering is drywall, larger sheets, fewer joints, cheaper. Since a properly built membrane shower keeps the moisture on the top side of the membrane, the drywall stays dry, and works fine. If it leaked, while the cbu wouldn't care, the structure would have problems, so leaks are a problem regardless, so choose whatever makes you feel happy, and don't look back second guessing. CBU works, too, but remember to wipe it down with a wet sponge first to take off the dust and to help prevent it sucking all of the moisture out of the thinset making installation harder and giving you less time. Other membranes, follow the manufacturer's recommendation on wall structure. A sheet membrane is sort of like putting up wallpaper, except it isn't critical matching patterns and an overlap is okay (you need one, whether it is the main sheet, or the manufactuer's banding material that can be added after or before the main sheets are applied, as long as you get the specified minimum overlap). The key with any membrane sheeting is to get the thinset mixed properly, and to use the proper premium type specified, and last, to pull a bit back off to check for proper coverage. The Kerdi drain is quite flexible as the square holding the grate can be easily moved during tiling to minimize cuts around it. My last one used 2x2 tile, and I was able to just cut four of them out of the mat and slide the center to perfectly align the gap...very neat and easy.

If you're using the Schluter products (Kerdi), you could get a 48x48 Schluter shower pan and cut it down to size. They're made to be cutable, so you'd just take 6" off 2 edges to get your 3x4 pan. This would save you the hassle/dry time of doing a mud bed.

There may be other cut-able pans on the market, I'm not familiar with them if there are. These Schluter pans require Kerdi over them and a Kerdi Drain to make a water-tight system. Maybe you can use other products with their pan, but I don't know about that, I just use the complete Schluter system, as it was designed to be used all together.

If you're going that route, you might as well just buy the whole shower kit and get everything in one shot. These generally run about $600.

Lemme save JW the hassle, and tell you right now that he thinks they're junk, they're overpriced, they're marketing hype, that Jim and I are getting paid by Schluter to hock their junk, etc. Its all bullshit, but that's what you're about to hear.

Choose the product you like (all of the ones JW likes are good products as well, if installed correctly), and install it properly, and you'll be fine.

IF the waterproofing membrane was also a wear surface (it is most certainly isn't), then thickness might be an issue. ALL are designed to be covered up with a wear surface, and MUST be protected prior to that happening. GoreTEx (TM) is MUCH thinner than Kerdi, and it works fine - because it isn't the wear surface - you NEVER see it as a top layer in clothing. Not saying GoreTex (TM) is a suitable tiling substrate, but this thickness argument just doesn't hold much water (pun intended!) with me. In a real situation, a thicker membrane can make corners harder to keep nice and flat. They ALL can get a hole poked into them, and if it does, it's poor workmanship. They ALL can be fixed, if that happens. ALL of the available membranes that have been approved (Kerdi has, along with many others) include a phrase like 'installed per manufactuer's instructions' that's part of the approval. Schluter recommends drywall, Kerdi is an approved method of waterproofing. Now, if you have a local code that doesn't allow it, it will work equally well installed over cbu, deckmud, a mudded wall, etc. It is NOT approved for use directly over wood, though, but most (all?) aren't. Choose whatever you prefer, but some people's rants against any one particular product are one person's rant, not the industries.

Thicker TVs make good designer statements and hold up better to their secondary use as a dartboard (when your team is doing poorly)
Thicker underwear are nice and comfy
Thicker glasses make for better vision (and more comfort on your face)
Thicker phones fit in my pocket better
Thicker skulls make smarter people

JW, I am the tilesetter, plumber, framer and electrician on this project. So I'm learning a lot. The framing is straight and square, tho there may be a few more pieces of wood than an old pro woulda used. The last piece of Romex I ran looks better than the first, but they all passed inspection. I'm kinda proud of the copper in the crawl space. Looks almost like I knew what I was doing. But once I'm all done, all anyone will see is the tile. (Cr@p, I think I mighta made myself a little nervous there.)

Time isn't that important, as I'm mostly working on the weekends. Money always counts, but I'll pay a little more for DIY friendly, if not idiot proof.

The reason WHY drywall is allowed, is it is NOT in a wet area when Kerdi is properly installed. There should be no vapor or liquid water that gets to the drywall from the wet area, therefore not a wet area.

From the Kerdi shower installation manual, it says solid backing materials for installing Kerdi, then, the section that describes what those suitable materials are (sorry, it didn't copy/paste with all the formatting, but it's all there):Solid Backing Materials

Gypsum wallboard – ASTM C1396/C1396M

Cementitious backer unit – ANSI A118.9 or ASTM C1325

Fiber-cement underlayment – ASTM C1288

Fiber-reinforced water-resistant gypsum backerboard/underlayment –

ASTM C1278

Coated glass mat water-resistant gypsum backerboard – ASTM C1178

Portland cement mortar – ANSI A108.1B

Concrete

Masonry

So, pick one that makes you and your local inspector happy, but ANY of these are approved.

Drywall is not permitted in wet zones. You might apply Kerdi over the backsplash near your sink or behind your stove but not in your shower.

In Europe Kerdi DS is used for primary wet zones (showers) and steam applications. Kerdi is used elsewhere.

Many liquid membranes also list drywall as an acceptable substrate but you would be equally outside of industry standards if used in a shower.

Best thing to do is to phone the TTMAC or purchase their specification guide. Drywall is listed only in non-wet zones.

This is really just common sense and Jim you site the proper rules when you choose. I would imagine you have a specification guide handy. Why not open it up?

JW

Click to expand...

Question... why would it matter? Lets for a minute leave Kerdi and all of its "problems" out of the picture. And lets have an answer that isn't just about "approved uses," but an actual rational thinking answer.

If your showers are so perfectly waterproof, who gives a crap if there's drywall behind it? It's only function is to provide a stable surface to attach the waterproofing to. Drywall is an acceptable substrate for backsplashes and other tile applications, so reason would state that it would be a sufficient substrate for a shower, if it was water tight. I thought your waterproofing was perfect, so the drywall behind a waterproof shower would actually be the best place to install it, as everywhere else, its exposed to a higher level of moisture and has a higher chance of becoming a mold problem.

That said, I'm not advocating it as a substrate behind anything that it is not specified as acceptable by the manufacturer. Kerdi specifies it as an acceptable backing. It is not acceptable to use as a tile backer w/o waterproofing in a shower, which would be a "wet zone"... can't tell you how many times I've seen that... "Ceramic tile is waterproof, right?"

Re things like glass tile. The Kerdi instructions say to call the tile manufacturer AND Schluter to come up with a suitable workaround, if it is possible. Since the requirements can be quite stringent, and you want a warranty from both the tile and the membrane user, that collaberation is required. Chances are, you can get a suitable, warranteed install, but you need to ask. Since the exact solution may vary, they require the collaberation consulation before approval. Just like you may need approval from your local building inspector if you want to do something outside the norm. If that's too much trouble, use a different product.

I love how much confidence you have in your perfect waterproofing. Properly waterproofed drywall behind a shower wall will NEVER grow mold. The MR gyp board that you put next to the shower is 10 times as likely to mold. Simple as that.

Don't install waterproofing on drywall that the manufacturer doesn't allow.

Your code reference is for Tile on Gyp board, thinset method. Not tile on gyp board, waterproofing then thinset method. Clearly its a dumb-ass idea to put up drywall and then tile in a shower. I tear those out from time to time, especially in tub surrounds. That is a different installation.

Turns out OSB is not an acceptable roofing surface, unless you put a proper waterproof roof over top of it. Hmm... odd how that works, eh?

If you don't want to use it, put in CMU, form a mold and pour a monolithic slab of concrete and use a pool liner before waterproofing, whatever makes you happy. Kerdi over drywall is accepted in the US, maybe Canada is different.